How to gain weight fast? How to gain weight fast in 1 week? How to gain muscle fast? How to gain weight and muscle for skinny guys? how to gain muscle? If these are the questions popping in your mind, I can help you. Though 1 week is too less a time to gain weight but I can surely help you how one and gradually increase healthy weight. Calories consumed per day should be greater than the Calories burnt per day to GAIN WEIGHT. We should aim to increase our weight in a healthy way.